The invention relates to a tool for use with a bone anchor. The bone anchor includes an anchoring section and a receiving part for receiving a rod to be connected to the anchoring section and a locking element. The tool is particularly applicable in spinal surgery, for example for the fixation of a rod to pedicle screws.
A known tool 100 is shown in FIGS. 19 and 20 in connection with polyaxial screws 101 and 102, which are connected via a rod 103. The tool 100 includes a counter-holding portion 104 with a handle 105 and a screw driver portion 106. The screw driver portion 106 is rotatable with respect to the counter-holding portion 104 and also comprises a handle 107. The screw driver portion 106 has a tip portion (not shown) that engages a locking screw 108 of the polyaxial screw 101 for fixation of the rod 103 within the receiving portion 109. The counter-holding portion 104 engages the receiving portion 109 and holds the receiving portion during tightening of the locking screw 108. The tightening torque which is necessary for finally tightening the locking screw 108 is typically in the range of approximately 7 to 15 Nm. The counter-holding portion 104 is advantageous in particular for counter-holding such high tightening torques. However, since the counter-holding portion acts at least partially onto the rod, the known tool is not suitable for flexible rods, for example for rods made of an elastomer material such as polycarbonate urethane (PCU), since the loads would lead to deformations which may damage the rod. Further, sensitive handling with two hands is difficult when applying high tightening torques.
A tool which has a counter-holding portion that engages the receiving portion of a bone anchor in a positive fit manner is known from European Patent Application EP 1 726 264.